Alvaro Herrera <alvherre@commandprompt.com> writes:
> update pk set id = max(id) + 2;
I'm fairly sure this query is illegal per spec. There are ancient
discussions in the archives about whether aggregates in an UPDATE target
list can have a consistent interpretation or not. We never found one,
but never got around to disallowing it either. Maybe it's time. If you
try it with something like sum() you don't get a crash, but you do get
rather bizarre behavior.
Having said that, this may well expose a bug in the MAX-optimization
code that has consequences for more useful queries. I'll take a look
later today if no one beats me to it.
regards, tom lane